The overall objective of this project is to determine the contribution that dental amalgam restorations make to the total body burden of mercury in children. The contractor will collect and assay exhaled air, saliva, blood and urine samples from participants in the New England Research Institutes/Forsyth Trial (NERIFT) and will collect and analyze quantitative data from these samples. Specific objectives of the study are to determine the contribution of amalgam to mercury present in biological media such as urine and plasma. The contractor will develop a stable isotope tracer, install the tracer in dental amalgams in amounts that will provide a measurable increase over and above its natural abundance level in urine and plasma, and will develop a tracer that will produce sensitive and precise measurement of mercury levels by mass spectrometry in adults and children. The contractor will select the stable isotope that gives the best cost/efficiency ratio as a tracer; determine the sensitivity and precision of the mass spectrometer to be used in the study; develop the technology to prepare amalgam enriched in the 204Hg isotope from the 204 Hg delivered as mercuric oxide powder from Oak Ridge laboratory; develop procedures to minimize the amount of 204Hg to be added to each filling; test the filling in vitro for release of 204 Hg; test adult volunteers to determine if 204Hg can be measured in exhaled air, saliva, plasma and urine; use the information obtained in aims 1-6 to test children; and conduct data analysis.